Reflective layer obtained by immobilizing cholesteric liquid crystalline phase

ABSTRACT

Provided are a method for producing a reflective layer having excellent diffuse reflectivity and a reflective layer having excellent diffuse reflectivity. The method for producing a reflective layer of the present invention includes Step 1 of applying a composition containing a liquid crystal compound and a chiral agent onto a substrate and heating the applied composition to align the liquid crystal compound into a cholesteric liquid crystalline phase state, and Step 2 of forming a reflective layer by cooling or heating the composition so that the helical twisting power of the chiral agent contained in the composition in the cholesteric liquid crystalline phase state increases by 5% or more.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of PCT International Application No.PCT/JP2017/010004 filed on Mar. 13, 2017, which claims priority under 35U.S.C. § 119(a) to Japanese Patent Application No. 2016-063809 filed onMar. 28, 2016 and Japanese Patent Application No. 2017-039430 filed onMar. 2, 2017. Each of the above applications is hereby expresslyincorporated by reference, in its entirety, into the presentapplication.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a method for producing a reflectivelayer and a reflective layer.

2. Description of the Related Art

A layer obtained by fixing a cholesteric liquid crystalline phase isknown as a layer having a property of selectively reflecting eitherdextrorotatory circularly polarized light or levorotatory circularlypolarized light in a specific wavelength range. For this reason, it hasbeen developed for various purposes; for example, it is used as a phasedifference layer (JP2005-49866A). In JP2005-49866A, the direction of analignment regulating force of an alignment film is set in a randomstate, and therefore the direction of a director of a liquid crystalcompound in contact with the alignment film is made random.

SUMMARY OF THE INVENTION

On the other hand, expansion of the viewing angle is required from theviewpoint of applying a layer obtained by fixing a cholesteric liquidcrystalline phase to a projected image display member such as aprojection screen.

More specifically, in the case where light is incident from the normaldirection of the surface of the layer obtained by fixing a cholestericliquid crystalline phase, either dextrorotatory circularly polarizedlight or levorotatory circularly polarized light is selectivelyreflected. At that time, in the case where the reflection is made notonly in the normal direction but also in the oblique direction, it leadsto an improvement in visibility from the oblique direction. In otherwords, the reflective layer is required to have excellentcharacteristics in which incident light is reflected in variousdirections (so-called diffuse reflectivity).

The present inventors have prepared a reflective layer using thealignment film described in JP2005-49866A without subjecting thereflective layer to a rubbing treatment and studied diffuse reflectivityof the thus-prepared reflective layer. As a result, the diffusereflectivity did not satisfy the recently required level and therefore afurther improvement was necessary.

In view of the above circumstances, an object of the present inventionis to provide a method for producing a reflective layer having excellentdiffuse reflectivity and a reflective layer having excellent diffusereflectivity.

As a result of extensive studies to achieve the foregoing object, thepresent inventors have found that a reflective layer having desiredcharacteristics can be produced by carrying out a treatment forincreasing the helical twisting power (HTP) of a chiral agent by apredetermined amount.

That is, the present inventors have found that the foregoing object canbe achieved by the following configuration.

[1] A method for producing a reflective layer, comprising: Step 1 ofapplying a composition containing a liquid crystal compound and a chiralagent onto a substrate and heating the applied composition to align theliquid crystal compound into a cholesteric liquid crystalline phasestate, and

Step 2 of forming a reflective layer by cooling or heating thecomposition so that the helical twisting power of the chiral agentcontained in the composition in the cholesteric liquid crystalline phasestate increases by 5% or more.

[2] The method for producing a reflective layer according to [1], inwhich the composition is cooled or heated in Step 2 so that the helicaltwisting power of the chiral agent increases by 10% or more.

[3] The method for producing a reflective layer according to [1] or [2],in which the composition is cooled or heated in Step 2 so that, in across section of a coating layer formed in Step 1, a bright portion anda dark portion derived from the cholesteric liquid crystalline phase arechanged into a state not parallel to the substrate.

[4] The method for producing a reflective layer according to [3], inwhich the composition is cooled or heated in Step 2 so that, in thecross section of the coating layer formed in Step 1, the bright portionand the dark portion derived from the cholesteric liquid crystallinephase are wave-like.

[5] The method for producing a reflective layer according to any one of[1] to [4], in which the liquid crystal compound is a liquid crystalcompound having a polymerizable group, the composition is subjected to acuring treatment to form a reflective layer obtained by immobilizing acholesteric liquid crystalline phase in Step 2, and the method furthercomprises Step 3 of subjecting the composition to a curing treatment toform a reflective layer obtained by immobilizing a cholesteric liquidcrystalline phase, after Step 2.

[6] The method for producing a reflective layer according to [5], inwhich the immobilization of the cholesteric liquid crystalline phase inStep 2 or the immobilization of the cholesteric liquid crystalline phasein Step 3 is to immobilize the structure after cooling or heating thecomposition.

[7] The method for producing a reflective layer according to [5] or [6],in which the immobilization of the cholesteric liquid crystalline phasein Step 2 or the immobilization of the cholesteric liquid crystallinephase in Step 3 is carried out by a polymerization reaction with lightirradiation.

[8] The method for producing a reflective layer according to [7], inwhich the polymerization reaction with light irradiation is a radicalpolymerization reaction.

[9] The method for producing a reflective layer according to any one of[1] to [8], in which the composition is cooled or heated in Step 2 sothat the helical twisting power of the chiral agent increases by 12% ormore.

[10] The method for producing a reflective layer according to any one of[1] to [9], in which the composition is cooled in Step 2 so that thetemperature of the composition decreases by 30° C. or higher.

[11] The method for producing a reflective layer according to any one of[1] to [10], in which the composition applied onto the substrate has afilm thickness of 0.1 to 20 μm.

[12] The method for producing a reflective layer according to any one of[1] to [11], in which the composition is cooled or heated in Step 2 sothat the helical twisting power of the chiral agent is 20 or more.

[13] The method for producing a reflective layer according to any one of[1] to [12], in which one or more of the compounds constituting thecomposition have a plurality of polymerizable groups and the totalcontent of the compound having the plurality of polymerizable groups inthe composition is 80% by mass or more based on the total solid contentin the composition.

[14] The method for producing a reflective layer according to any one of[1] to [13], in which the composition containing a liquid crystalcompound and a chiral agent further contains an alignment control agent.

[15] The method for producing a reflective layer according to any one of[1] to [14], in which the composition is cooled in Step 2 at a coolingrate at which a maximum value is 1° C. or higher per second.

[16] A reflective layer obtained by immobilizing a cholesteric liquidcrystalline phase, in which, in a cross section of the reflective layer,a bright portion and a dark portion derived from the cholesteric liquidcrystalline phase are wave-like, and

a surface of the reflective layer has periodic roughness which isdifferent in phase from the wave of the bright portion and the darkportion of the cross section of the reflective layer.

[17] The reflective layer according to [16], in which the roughness onthe surface is formed by changing the alignment of the cholestericliquid crystalline phase.

[18] The reflective layer according to [16] or [17], in which a pitch ofthe roughness on the surface is 0.5 to 10 μm.

[19] The reflective layer according to any one of [16] to [18], in whicha height of the roughness on the surface is 1 to 500 nm.

According to the present invention, it is possible to provide a methodfor producing a reflective layer having excellent diffuse reflectivityand a reflective layer having excellent diffuse reflectivity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram in the case where a cross section of alayer in a general cholesteric liquid crystalline phase state isobserved by a scanning electron microscope (SEM).

FIG. 2 is a schematic diagram in the case where a cross section of areflective layer produced by a production method of the presentinvention is observed by SEM.

FIG. 3 is a schematic diagram in the case where the cross section of thereflective layer of the present invention is observed by SEM.

FIG. 4 is a polarization microscopic image of a reflective layer 1.

FIG. 5 is a cross-sectional SEM observation diagram of the reflectivelayer 1.

FIG. 6 is a schematic diagram of an apparatus used for diffusereflectivity evaluation.

FIG. 7 is a surface analysis result of a shape measuring lasermicroscope of a reflective layer 13.

FIG. 8 is a cross-sectional SEM observation diagram of a reflectivelayer 15.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described in detail. In thepresent specification, the numerical range expressed by using “to” meansa range including numerical values described before and after “to” as alower limit value and an upper limit value, respectively.

Further, in the present specification, the term “(meth)acrylate” is anotation expressing both acrylate and methacrylate, the term“(meth)acryloyl group” is a notation expressing both acryloyl group andmethacryloyl group, and the term “(meth)acrylic” is a notationexpressing both acrylic and methacrylic.

In the production method of a reflective layer of the present invention,a reflective layer having excellent diffuse reflectivity can be formedby subjecting the composition in the cholesteric liquid crystallinephase state to a cooling treatment or heat treatment so that the helicaltwisting power of the chiral agent increases by 5% or more.

Although the reason that such a reflective layer having excellentdiffuse reflectivity is obtained is not clear in detail, the presentinventors speculate as follows.

First, FIG. 1 shows a schematic cross-sectional view in the case where alayer of a composition in a general cholesteric liquid crystalline phasestate is disposed on a substrate. As shown in FIG. 1, in the case wherea cross section of a layer 12 a of the composition in the cholestericliquid crystalline phase state disposed on a substrate 10 is observed bya scanning electron microscope (SEM), normally, stripe patterns of abright portion 14 and a dark portion 16 are observed. That is, a layeredstructure in which the bright portion 14 and the dark portion 16 arealternately laminated is observed in the cross section of the layer 12 aof the composition in the cholesteric liquid crystalline phase state.

One bright portion 14 and two dark portions 16 disposed above and belowthe one bright portion 14 in FIG. 1 correspond to one helical pitch.

Generally, as shown in FIG. 1, the stripe pattern (layered structure) ofthe bright portion 14 and the dark portion 16 is formed to be parallelto the surface of the substrate 10. In such an aspect, in the case wherelight is incident from the normal direction of the layer 12 a of thecomposition in the cholesteric liquid crystalline phase state, light isreflected in the normal direction, but light is hardly reflected in theoblique direction, which results in poor diffuse reflectivity (seearrows in FIG. 1).

On the other hand, according to the production method of the presentinvention, by subjecting the composition in the cholesteric liquidcrystalline phase state to a cooling treatment or heat treatment so thatthe helical twisting power of the chiral agent increases by 5% or more,the twist of the liquid crystal compound becomes stronger, and thereforethe layer in the cholesteric liquid crystalline phase changes so as tobe tilted. More specifically, by subjecting the layer 12 a of thecomposition in the cholesteric liquid crystalline phase state shown inFIG. 1 to a predetermined treatment, as shown in FIG. 2, a layer 12 b inwhich the bright portion 14 and the dark portion 16 have a wave-likestructure (undulated structure) is obtained. In the case where light isincident on the layer 12 b having such a wave-like structure (roughnessstructure) from the normal direction of the layer 12 b having awave-like structure, as shown in FIG. 2, a part of the incident light isreflected in an oblique direction since there is a region where thehelical axis of the liquid crystal compound is inclined (see arrows inFIG. 2). That is, according to the production method of the presentinvention, a reflective layer having excellent diffuse reflectivity canbe obtained.

The method for producing a reflective layer of the present invention hasat least the following steps 1 and 2.

Step 1: a step of applying a composition containing a liquid crystalcompound and a chiral agent onto a substrate and heating the appliedcomposition to align the liquid crystal compound into a cholestericliquid crystalline phase state

Step 2: a step of cooling or heating the composition so as to form areflective layer so that the helical twisting power of the chiral agentcontained in the composition in the cholesteric liquid crystalline phasestate increases by 5% or more

Hereinafter, the materials used in each step and the procedure of eachstep will be described in detail.

<Step 1>

Step 1 is a step of applying a composition containing a liquid crystalcompound and a chiral agent onto a substrate and heating the appliedcomposition to align the liquid crystal compound into a cholestericliquid crystalline phase state.

Hereinafter, the substrate and the composition used in the present stepwill be described first in detail, and then the procedure of the stepswill be described in detail.

(Substrate)

The substrate is a plate that supports a layer of the compositiondescribed below. Among others, a transparent substrate is preferable.The transparent substrate is intended to refer to a substrate having atransmittance of visible light of 60% or more, and the transmittancethereof is preferably 80% or more and more preferably 90% or more.

The material constituting the substrate is not particularly limited, andexamples thereof include a cellulose-based polymer, apolycarbonate-based polymer, a polyester-based polymer, a (meth)acrylicpolymer, a styrene-based polymer, a polyolefin-based polymer, a vinylchloride-based polymer, an amide-based polymer, an imide-based polymer,a sulfone-based polymer, a polyether sulfone-based polymer, and apolyether ether ketone-based polymer.

The substrate may contain various additives such as an ultraviolet (UV)absorber, a matting agent fine particle, a plasticizer, a deteriorationinhibitor, and a release agent.

In addition, the substrate preferably has low birefringence in thevisible light region. For example, the phase difference at a wavelengthof 550 nm of the substrate is preferably 50 nm or less and morepreferably 20 nm or less.

The thickness of the substrate is not particularly limited, but it ispreferably 10 to 200 μm and more preferably 20 to 100 μm from theviewpoint of thinning and handleability.

The thickness is intended to refer to an average thickness, and isobtained by measuring thicknesses at five places of the substrate andarithmetically averaging the measured values. Regarding the method ofmeasuring the thickness, the same applies to the thickness of areflective layer (layer 12 a of the composition in the cholestericliquid crystalline phase state) to be described later.

(Liquid Crystal Compound)

The type of the liquid crystal compound is not particularly limited.

Generally, liquid crystal compounds can be classified into a rod type(rod-like liquid crystal compound) and a disc type (discotic liquidcrystal compound, disk-like liquid crystal compound) depending on theshape thereof. Further, the rod type and the disk type each have a lowmolecular weight type and a high molecular weight type. The highmolecular weight generally refers to having a degree of polymerizationof 100 or more (Polymer Physics-Phase Transition Dynamics, Masao Doi,page 2, Iwanami Shoten, 1992). Any liquid crystal compound can be usedin the present invention. Two or more liquid crystal compounds may beused in combination.

The liquid crystal compound may have a polymerizable group. The type ofthe polymerizable group is not particularly limited, and a functionalgroup capable of addition polymerization reaction is preferable, and apolymerizable ethylenically unsaturated group or a cyclic polymerizablegroup is more preferable. More specifically, the polymerizable group ispreferably a (meth)acryloyl group, a vinyl group, a styryl group, anallyl group, an epoxy group, or an oxetane group, and more preferably a(meth)acryloyl group.

The liquid crystal compound is preferably a liquid crystal compoundrepresented by Formula (I) from the viewpoint that the reflective layerhas superior diffuse reflectivity.

Among these, from the viewpoint of superior diffuse reflectivity of thereflective layer, in the case where the number obtained by dividing thenumber of trans-1,4-cyclohexylene groups which may have a substituentrepresented by A by m is defined as mc, a liquid crystal compoundsatisfying mc>0.1 is preferable, and a liquid crystal compoundsatisfying 0.4≤mc≤0.8 is more preferable.

Note that mc is a number represented by the following calculationformula.mc=(the number of trans-1,4-cyclohexylene groups which may have asubstituent represented by A)÷m

In the formula,

A represents a phenylene group which may have a substituent or atrans-1,4-cyclohexylene group which may have a substituent, at least oneof A's represents a trans-1,4-cyclohexylene group which may have asubstituent,

L represents a single bond or a linking group selected from the groupconsisting of —CH₂O—, —OCH₂—, —(CH₂)₂OC(═O)—, —C(═O)O(CH₂)₂—, —C(═O)O—,—OC(═O)—, —OC(═O)O—, —CH═N—N═CH—, —CH═CH—, —C≡C—, —NHC(═O)—, —C(═O)NH—,—CH═N—, —N═CH—, —CH═CH—C(═O)O—, and —OC(═O)—CH═CH—, m represents aninteger of 3 to 12,

Sp¹ and Sp² each independently represent a single bond or a linkinggroup selected from the group consisting of a linear or branchedalkylene group having 1 to 20 carbon atoms and a group where one or twoor more —CH₂— in a linear or branched alkylene group having 1 to 20carbon atoms is substituted with —O—, —S—, —NH—, —N(CH₃)—, —C(═O)—,—OC(═O)—, or —C(═O)O—, and

Q¹ and Q² each independently represent a hydrogen atom or apolymerizable group selected from the group consisting of groupsrepresented by Formulae (Q-1) to (Q-5), provided that one of Q¹ and Q²represents a polymerizable group.

A is a phenylene group which may have a substituent or atrans-1,4-cyclohexylene group which may have a substituent. In thepresent specification, the phenylene group is preferably a 1,4-phenylenegroup.

At least one of A's is a trans-1,4-cyclohexylene group which may have asubstituent.

(m) number of A's may be the same as or different from each other.

m represents an integer of 3 to 12, preferably an integer of 3 to 9,more preferably an integer of 3 to 7, and still more preferably aninteger of 3 to 5.

The substituent which the phenylene group and thetrans-1,4-cyclohexylene group in Formula (I) may have is notparticularly limited, and examples thereof include substituents selectedfrom the group consisting of an alkyl group, a cycloalkyl group, analkoxy group, an alkyl ether group, an amide group, an amino group, ahalogen atom, and a group formed by combining two or more of thesesubstituents. Examples of the substituent include substituentsrepresented by —C(═O)—X³—Sp³-Q³ which will be described later. Thephenylene group and the trans-1,4-cyclohexylene group may have 1 to 4substituents. In the case of having two or more substituents, the two ormore substituents may be the same as or different from each other.

In the present specification, the alkyl group may be either linear orbranched. The number of carbon atoms in the alkyl group is preferably 1to 30, more preferably 1 to 10, and still more preferably 1 to 6.Examples of the alkyl group include a methyl group, an ethyl group, ann-propyl group, an isopropyl group, an n-butyl group, an isobutyl group,a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentylgroup, a neopentyl group, a 1,1-dimethylpropyl group, an n-hexyl group,an isohexyl group, a heptyl group, an octyl group, a nonyl group, adecyl group, an undecyl group, and a dodecyl group. The explanation ofthe alkyl group in the alkoxy group is also the same as the explanationon the foregoing alkyl group. Further, in the present specification,specific examples of the alkylene group in the case of being referred toas an alkylene group include divalent groups obtained by removing onehydrogen atom from each of the foregoing examples of the alkyl group.Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom, and an iodine atom.

In the present specification, the number of carbon atoms in thecycloalkyl group is preferably 3 or more and more preferably 5 or moreand is preferably 20 or less, more preferably 10 or less, still morepreferably 8 or less, and particularly preferably 6 or less. Examples ofthe cycloalkyl group include a cyclopropyl group, a cyclobutyl group, acyclopentyl group, a cyclohexyl group, a cycloheptyl group, and acyclooctyl group.

The substituent which the phenylene group and thetrans-1,4-cyclohexylene group may have is preferably a substituentselected from the group consisting of an alkyl group, an alkoxy group,and —C(═O)—X³—Sp³-Q³. Here, X³ represents a single bond, —O—, —S—, or—N(Sp⁴-Q⁴)- or represents a nitrogen atom forming a ring structuretogether with Q³ and Sp³. Sp³ and Sp⁴ each independently represent asingle bond or a linking group selected from the group consisting of alinear or branched alkylene group having 1 to 20 carbon atoms and agroup where one or two or more —CH₂— in a linear or branched alkylenegroup having 1 to 20 carbon atoms is substituted with —O—, —S—, —NH—,—N(CH₃)—, —C(═O)—, —OC(═O)—, or —C(═O)O—.

Q³ and Q⁴ each independently represent a hydrogen atom, a cycloalkylgroup, a group where one or two or more —CH₂— in a cycloalkyl group issubstituted with —O—, —S—, —NH—, —N(CH₃)—, —C(═O)—, —OC(═O)—, or—C(═O)O—, or any polymerizable group selected from the group consistingof groups represented by Formulae (Q-1) to (Q-5).

Specific examples of the group where one or two or more —CH₂— in acycloalkyl group is substituted with —O—, —S—, —NH—, —N(CH₃)—, —C(═O)—,—OC(═O)—, or —C(═O)O— include a tetrahydrofuranyl group, a pyrrolidinylgroup, an imidazolidinyl group, a pyrazolidinyl group, a piperidylgroup, a piperazinyl group, and a morpholinyl group. Among them, atetrahydrofuranyl group is preferable, and a 2-tetrahydrofuranyl groupis more preferable.

In Formula (I), L represents a single bond or a linking group selectedfrom the group consisting of —CH₂O—, —OCH₂—, —(CH₂)₂OC(═O)—,—C(═O)O(CH₂)₂—, —C(═O)O—, —OC(═O)—, —OC(═O)O—, —CH═CH—C(═O)O—, and—OC(═O)—CH═CH—. L is preferably —C(═O)O— or —OC(═O)—. (m) number of L'smay be the same as or different from each other.

Sp¹ and Sp² each independently represent a single bond or a linkinggroup selected from the group consisting of a linear or branchedalkylene group having 1 to 20 carbon atoms and a group where one or twoor more —CH₂— in a linear or branched alkylene group having 1 to 20carbon atoms is substituted with —O—, —S—, —NH—, —N(CH₃)—, —C(═O)—,—OC(═O)—, or —C(═O)O—. Sp¹ and Sp² are each independently preferably alinking group formed by combining one or two or more groups selectedfrom the group consisting of a linear alkylene group having 1 to 10carbon atoms to which a linking group selected from the group consistingof —P—, —OC(═O)—, and —C(═O)O— is bonded to both terminals thereof,—OC(═O)—, —C(═O)O—, —O—, and a linear alkylene group having 1 to 10carbon atoms, and more preferably a linear alkylene group having 1 to 10carbon atoms to which —O— is bonded to both terminals thereof.

Q¹ and Q² each independently represent a hydrogen atom or apolymerizable group selected from the group consisting of groupsrepresented by Formulae (Q-1) to (Q-5), provided that either one of Q¹and Q² represents a polymerizable group.

The polymerizable group is preferably an acryloyl group (Formula (Q-1))or a methacryloyl group (Formula (Q-2)).

Specific examples of the liquid crystal compound include a liquidcrystal compound represented by Formula (I-11), a liquid crystalcompound represented by Formula (I-21), and a liquid crystal compoundrepresented by Formula (I-31). In addition to the foregoing compounds,known compounds such as a compound represented by Formula (I) inJP2013-112631A, a compound represented by Formula (I) in JP2010-70543A,a compound represented by Formula (I) in JP2008-291218A, a compoundrepresented by Formula (I) in JP4725516B, a compound represented byFormula (II) in JP2013-087109A, a compound described in paragraph [0043]of JP2007-176927A, a compound represented by Formula (1-1) inJP2009-286885A, a compound represented by Formula (I) in WO2014/10325A,a compound represented by Formula (1) in JP2016-81035A, and a compoundrepresented by Formulae (2-1) and (2-2) in JP2016-121339A can bementioned.

A liquid crystal compound represented by Formula (I-11)

In the formula, R¹¹ represents a hydrogen atom, a linear or branchedalkyl group having 1 to 12 carbon atoms, or —Z¹²—SP¹²-Q¹²-Q¹²,

L¹¹ represents a single bond, —C(═O)O—, or —O(C═O)—,

L¹² represents —C(═O)O—, —OC(═O)—, or —CONR²—

R² represents a hydrogen atom or an alkyl group having 1 to 3 carbonatoms,

Z¹¹ and Z¹² each independently represent a single bond, —O—, —NH—,—N(CH₃)—, —S—, —C(═O)O—, —OC(═O)—, —OC(═O)O—, or —C(═O)NR¹²—

R¹² represents a hydrogen atom or —Sp¹²-Q¹²,

Sp¹¹ and Sp¹² each independently represent a single bond, a linear orbranched alkylene group having 1 to 12 carbon atoms which may besubstituted with Q¹¹, or a linking group obtained by substituting one ormore —CH₂— in a linear or branched alkylene group having 1 to 12 carbonatoms which may be substituted with Q¹¹ with —O—, —S—, —NH—, —N(Q¹¹)-,or —C(═O)—,

Q¹¹ represents a hydrogen atom, a cycloalkyl group, a group where one ormore —CH₂— in a cycloalkyl group is substituted with —O—, —S—, —NH—,—N(CH₃)—, —C(═O)—, —OC(═O)—, or —C(═O)O—, or a polymerizable groupselected from the group consisting of groups represented by Formulae(Q-1) to (Q-5),

Q¹² represents a hydrogen atom or a polymerizable group selected fromthe group consisting of groups represented by Formulae (Q-1) to (Q-5)

l¹¹ represents an integer of 0 to 2,

m¹¹ represents an integer of 1 or 2,

n¹¹ represents an integer of 1 to 3, and

a plurality of R¹¹'s, a plurality of L¹¹'s, a plurality of L¹²'s, aplurality of l¹¹'s, a plurality of Z¹¹'s, a plurality of Sp¹¹'s, and aplurality of Q¹¹'s may be respectively the same as or different fromeach other.

The liquid crystal compound represented by Formula (I-11) contains atleast one —Z¹²—Sp¹²-Q¹² in which Q¹² is a polymerizable group selectedfrom the group consisting of groups represented by Formulae (Q-1) to(Q-5), as R¹¹.

In addition, the liquid crystal compound represented by Formula (I-11)is preferably —Z¹¹—Sp¹¹-Q¹¹ in which Z¹¹ is —C(═O)O— or —C(═O)NR¹²— andQ¹¹ is a polymerizable group selected from the group consisting ofgroups represented by Formulae (Q-1) to (Q-5). The liquid crystalcompound represented by Formula (I-11) is preferably —Z¹²-Sp¹²-Q¹² inwhich Z¹² is —C(═O)O— or —C(═O)NR¹²—, and Q¹² is a polymerizable groupselected from the group consisting of groups represented by Formulae(Q-1) to (Q-5), as R¹¹.

The 1,4-cyclohexylene group contained in the liquid crystal compoundrepresented by Formula (I-11) is a trans-1,4-cyclohexylene group.

A suitable aspect of the liquid crystal compound represented by Formula(I-11) may be, for example, a compound in which L¹¹ is a single bond,l¹¹ is 1-(a dicyclohexyl group), and Q¹¹ is a polymerizable groupselected from the group consisting of groups represented by Formulae(Q-1) to (Q-5).

Another suitable aspect of the liquid crystal compound represented byFormula (I-11) may be, for example, a compound in which m¹¹ is 2, l¹¹ is0, and two R¹¹'s each represent —Z¹²-Sp¹²-Q¹², and Q¹² is apolymerizable group selected from the group consisting of groupsrepresented by Formulae (Q-1) to (Q-5).

The liquid crystal compound represented by Formula (I-21)

In the formula, Z²¹ and Z²² each independently represent atrans-1,4-cyclohexylene group which may have a substituent or aphenylene group which may have a substituent,

the above substituents are each independently 1 to 4 substituentsselected from the group consisting of —CO—X²¹-Sp²³-Q²³, an alkyl group,and an alkoxy group,

m21 represents an integer of 1 or 2, and n21 represents an integer of 0or 1,

in the case where m21 represents 2, n21 represents 0,

in the case where m21 represents 2, two Z²¹'s may be the same ordifferent,

at least one of Z²¹ or Z²² is a phenylene group which may have asubstituent,

L²¹, L²², L²³, L²⁴ each independently represent a single bond or alinking group selected from the group consisting of —CH₂O—, —OCH₂—,—(CH₂)₂OC(═O)—, —C(═O)O(CH₂)₂—, —C(═O)O—, —OC(═O)—, —OC(═O)O—,—CH═CH—C(═O)O—, and —OC(═O)—CH═CH—,

X²¹ represents —O—, —S—, or —N(Sp²⁵-Q²⁵)- or represents a nitrogen atomforming a ring structure together with Q²³ and Sp²³,

r²¹ represents an integer of 1 to 4,

Sp²¹, Sp²², Sp²³, and Sp²⁵ each independently represent a single bond ora linking group selected from the group consisting of a linear orbranched alkylene group having 1 to 20 carbon atoms and a group whereone or two or more —CH₂— in a linear or branched alkylene group having 1to 20 carbon atoms is substituted with —O—, —S—, —NH—, —N(CH₃)—,—C(═O)—, —OC(═O)—, or —C(═O)O—,

Q²¹ and Q²² each independently represent a polymerizable group selectedfrom the group consisting of groups represented by Formulae (Q-1) to(Q-5),

Q²³ represents a hydrogen atom, a cycloalkyl group, a group where one ortwo or more —CH₂— in a cycloalkyl group is substituted with —O—, —S—,—NH—, —N(CH₃)—, —C(═O)—, —OC(═O)—, or —C(═O)O—, any one polymerizablegroup selected from the group consisting of groups represented byFormulae (Q-1) to (Q-5), or a single bond in the case where X²¹ is anitrogen atom forming a ring structure together with Q²³ and Sp²³, and

Q²⁵ represents a hydrogen atom, a cycloalkyl group, a group where one ortwo or more —CH₂— in a cycloalkyl group is substituted with —O—, —S—,—NH—, —N(CH₃)—, —C(═O)−, —OC(═O)—, or —C(═O)O—, or any one polymerizablegroup selected from the group consisting of groups represented byFormulae (Q-1) to (Q-5), provided that in the case where Sp²⁵ is asingle bond, Q²⁵ is not a hydrogen atom.

It is also preferred that the liquid crystal compound represented byFormula (I-21) has a structure in which a 1,4-phenylene group and atrans-1,4-cyclohexylene group are alternately present. For example,preferred is a structure in which m21 is 2, n21 is 0, and Z²¹ is atrans-1,4-cyclohexylene group which may have a substituent from the Q²¹side or an arylene group which may have a substituent, or a structure inwhich m21 is 1, n21 is 1, Z²¹ is an arylene group which may have asubstituent, and Z²² is an arylene group which may have a substituent.

A liquid crystal compound represented by Formula (I-31);

In the formula, R³¹ and R³² each independently represent an alkyl group,an alkoxy group, and a group selected from the group consisting of—C(═O)—X³¹-Sp³³-Q³³,

n31 and n32 each independently represent an integer of 0 to 4,

X³¹ represents a single bond, —O—, —S—, or —N(Sp³⁴-Q³⁴)- or represents anitrogen atom forming a ring structure together with Q³³ and Sp³³,

Z³¹ represents a phenylene group which may have a substituent,

Z³² represents a trans-1,4-cyclohexylene group which may have asubstituent or a phenylene group which may have a substituent,

the above substituents are each independently 1 to 4 substituentsselected from the group consisting of an alkyl group, an alkoxy group,and —C(═O)—X³¹-Sp³³-Q³³,

m31 represents an integer of 1 or 2, and m32 represents an integer of 0to 2,

in the case where m31 and m32 represent 2, two Z³¹'s and Z³²'s may bethe same or different,

L³¹ and L³² each independently represent a single bond or a linkinggroup selected from the group consisting of —CH₂O—, —OCH₂—,—(CH₂)₂OC(═O)—, —C(═O)O(CH₂)₂—, —C(═O)O—, —OC(═O)—, —OC(═O)O—,—CH═CH—C(═O)O—, and —OC(═O)—CH═CH—,

Sp³¹, Sp³², Sp³³, and Sp³⁴ each independently represent a single bond ora linking group selected from the group consisting of a linear orbranched alkylene group having 1 to 20 carbon atoms and a group whereone or two or more —CH₂— in a linear or branched alkylene group having 1to 20 carbon atoms is substituted with —O—, —S—, —NH—, —N(CH₃)—,—C(═O)—, —OC(═O)—, or —C(═O)O—,

Q³¹ and Q³² each independently represent a polymerizable group selectedfrom the group consisting of groups represented by Formulae (Q-1) to(Q-5), and

Q³³ and Q³⁴ each independently represent a hydrogen atom, a cycloalkylgroup, a group where one or two or more —CH₂— in a cycloalkyl group issubstituted with —O—, —S—, —NH—, —N(CH₃)—, —C(═O)—, —OC(═O)—, or—C(═O)O—, or any one polymerizable group selected from the groupconsisting of groups represented by Formulae (Q-1) to (Q-5), providedthat Q³³ may represent a single bond in the case of forming a ringstructure together with X³¹ and Sp³³, and Q³⁴ is not a hydrogen atom inthe case where Sp³⁴ is a single bond.

As the liquid crystal compound represented by Formula (I-31),particularly preferable compounds include a compound in which Z³² is aphenylene group and a compound in which m32 is 0.

It is also preferred that the compound represented by Formula (I) has apartial structure represented by Formula (II).

In Formula (II), black circles indicate the bonding positions with othermoieties of Formula (I). The partial structure represented by Formula(II) may be included as a part of the partial structure represented byFormula (III) in Formula (I).

In the formula, R₁ and R₂ are each independently a group selected fromthe group consisting of a hydrogen atom, an alkyl group, an alkoxygroup, and a group represented by —C(═O)—X³-Sp³-Q³. Here, X³ representsa single bond, —O—, —S—, or —N(Sp⁴-Q⁴)- or represents a nitrogen atomforming a ring structure together with Q³ and Sp³. X³ is preferably asingle bond or —O—. R₁ and R₂ are preferably —C(═O)—X³-Sp³-Q³. It isalso preferred that R₁ and R₂ are the same. The bonding position of eachof R₁ and R₂ to the phenylene group is not particularly limited.

Sp³ and Sp⁴ each independently represent a single bond or a linkinggroup selected from the group consisting of a linear or branchedalkylene group having 1 to 20 carbon atoms and a group where one or twoor more —CH₂— in a linear or branched alkylene group having 1 to 20carbon atoms is substituted with —O—, —S—, —NH—, —N(CH₃)—, —C(═O)—,—OC(═O)—, or —C(═O)O—. Sp³ and Sp⁴ are each independently preferably alinear or branched alkylene group having 1 to 10 carbon atoms, morepreferably a linear alkylene group having 1 to 5 carbon atoms, and stillmore preferably a linear chain alkylene group having 1 to 3 carbonatoms.

Q³ and Q⁴ each independently represent a hydrogen atom, a cycloalkylgroup, a group where one or two or more —CH₂— in a cycloalkyl group issubstituted with —O—, —S—, —NH—, —N(CH₃)—, —C(═O)—, —OC(═O)—, or—C(═O)O—, or any one polymerizable group selected from the groupconsisting of groups represented by Formulae (Q-1) to (Q-5).

It is also preferred that the compound represented by Formula (I) has,for example, a structure represented by Formula (II-2).

In the formula, A¹ and A² each independently represent a phenylene groupwhich may have a substituent or a trans-1,4-cyclohexylene group whichmay have a substituent, and the above substituents are eachindependently 1 to 4 substituents selected from the group consisting ofan alkyl group, an alkoxy group, and —C(═O)—X³-Sp³-Q³,

L¹, L², and L³ each represent a single bond or a linking group selectedfrom the group consisting of —CH₂O—, —OCH₂—, —(CH₂)₂OC(═O)—,—C(═O)O(CH₂)₂—, —C(═O)O—, —OC(═O)—, —OC(═O)O—, —CH═CH—C(═O)O—, and—OC(═O)—CH═CH—, and

n1 and n2 each independently represent an integer of 0 to 9, and n1+n2is 9 or less.

Each of Q¹, Q², Sp¹, and Sp² has the same definition as that of eachgroup in Formula (I). Each of X³, Sp³, Q³, R¹, and R² has the samedefinition as that of each group in Formula (II).

As the liquid crystal compound which is a liquid crystal compoundrepresented by Formula (I) and satisfies 0.4≤mc≤0.8, the followingcompounds are exemplified.

Two or more liquid crystal compounds may be used in combination. Forexample, two or more liquid crystal compounds represented by Formula (I)may be used in combination.

Among these, it is preferable to use a liquid crystal compound which isa liquid crystal compound represented by Formula (I) and satisfies0.1<mc<0.3, together with the liquid crystal compound which is a liquidcrystal compound represented by Formula (I) and satisfies 0.4≤mc≤0.8.

As the liquid crystal compound which is a liquid crystal compoundrepresented by Formula (I) and satisfies 0.1<mc<0.3, the followingcompounds are exemplified.

As the liquid crystal compound for use in the present invention, acompound represented by Formula (IV) and described in JP2014-198814A, inparticular, a polymerizable liquid crystal compound having one(meth)acrylate group represented by Formula (IV) is also suitably used.

In Formula (IV), A¹ represents an alkylene group having 2 to 18 carbonatoms, in which one CH₂ in the alkylene group or two or morenon-adjacent CH₂ may be substituted with —O—;

Z¹ represents —C(═O)—, —O—C(═O)—, or a single bond;

Z² represents —C(═O)— or —C(═O)—CH═CH—;

R¹ represents a hydrogen atom or a methyl group;

R² represents a hydrogen atom, a halogen atom, a linear alkyl grouphaving 1 to 4 carbon atoms, a methoxy group, an ethoxy group, a phenylgroup which may have a substituent, a vinyl group, a formyl group, anitro group, a cyano group, an acetyl group, an acetoxy group, anN-acetylamide group, an acryloylamino group, an N,N-dimethylamino group,a maleimide group, a methacryloylamino group, an allyloxy group, anallyloxycarbamoyl group, an N-alkyloxycarbamoyl group in which the alkylgroup has 1 to 4 carbon atoms, an N-(2-methacryloyloxyethyl)carbamoyloxygroup, an N-(2-acryloyloxyethyl)carbamoyloxy group, or a structurerepresented by Formula (IV-2); and

L¹, L², L³, and L⁴ each independently represent an alkyl group having 1to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, analkoxycarbonyl group having 2 to 5 carbon atoms, an acyl group having 2to 4 carbon atoms, a halogen atom, or a hydrogen atom, and at least oneof L¹, L², L³, or L⁴ represents a group other than a hydrogen atom.—Z⁵-T-Sp-P  Formula (IV-2)

In Formula (IV-2), P represents an acryl group, a methacryl group, or ahydrogen atom, and Z⁵ represents a single bond, C(═O)O—, —OC(═O)—,—C(═O)NR¹— (where R¹ represents a hydrogen atom or a methyl group),—NR¹C(═O)—, —C(═O)S—, or —SC(═O)—, T represents 1,4-phenylene, and Sprepresents a divalent aliphatic group having 1 to 12 carbon atoms whichmay have a substituent, in which one CH₂ in the aliphatic group or twoor more non-adjacent CH₂ may be substituted with —O—, —S—, —OC(═O)—,—C(═O)O—, or —OC(═O)O—.

The compound represented by Formula (IV) is preferably a compoundrepresented by Formula (V).

In Formula (V), n1 represents an integer of 3 to 6;

R¹¹ represents a hydrogen atom or a methyl group;

Z¹² represents —C(═O)— or —C(═O)—CH═CH—; and

R¹² represents a hydrogen atom, a linear alkyl group having 1 to 4carbon atoms, a methoxy group, an ethoxy group, a phenyl group, anacryloylamino group, a methacryloylamino group, an allyloxy group, or astructure represented by Formula (IV-3).—Z⁵¹-T-Sp-P  Formula (IV-3)

In Formula (IV-3), P represents an acryl group or a methacryl group;

Z⁵¹ represents —C(═O)O— or —OC(═O)—; T represents 1,4-phenylene; and

Sp represents a divalent aliphatic group having 2 to 6 carbon atomswhich may have a substituent. One CH₂ in this aliphatic group or two ormore non-adjacent CH₂ may be substituted with —O—, —OC(═O)—, —C(═O)O—,or —OC(═O)O—.

n1 represents an integer of 3 to 6, preferably 3 or 4.

Z¹² represents —C(═O)— or —C(═O)—CH═CH— and preferably represents—C(═O)—.

R¹² is a hydrogen atom, a linear alkyl group having 1 to 4 carbon atoms,a methoxy group, an ethoxy group, a phenyl group, an acryloylaminogroup, a methacryloylamino group, an allyloxy group, or a grouprepresented by Formula (IV-3), preferably represents a methyl group, anethyl group, a propyl group, a methoxy group, an ethoxy group, a phenylgroup, an acryloylamino group, a methacryloylamino group, or a grouprepresented by Formula (IV-3), and more preferably represents a methylgroup, an ethyl group, a methoxy group, an ethoxy group, a phenyl group,an acryloylamino group, a methacryloylamino group, or a structurerepresented by Formula (IV-3).

Specific examples of the compound represented by Formula (IV) are shownbelow. However, in the present invention, the compound represented byFormula (IV) is not limited thereto.

As the liquid crystal compound for use in the present invention, acompound represented by Formula (VI) and described in JP2014-198814A, inparticular, a liquid crystal compound having no (meth)acrylate grouprepresented by Formula (VI) is also suitably used.

In Formula (VI), Z³ represents —C(═O)— or —CH═CH—C(═O)—;

Z⁴ represents —C(═O)— or —C(═O)—CH═CH—;

R³ and R⁴ each independently represent a hydrogen atom, a halogen atom,a linear alkyl group having 1 to 4 carbon atoms, a methoxy group, anethoxy group, an aromatic ring which may have a substituent, acyclohexyl group, a vinyl group, a formyl group, a nitro group, a cyanogroup, an acetyl group, an acetoxy group, an acryloylamino group, anN,N-dimethylamino group, a maleimide group, a methacryloylamino group,an allyloxy group, an allyloxycarbamoyl group, an N-alkyloxycarbamoylgroup in which the alkyl group has 1 to 4 carbon atoms, anN-(2-methacryloyloxyethyl)carbamoyloxy group, anN-(2-acryloyloxyethyl)carbamoyloxy group, or a structure represented byFormula (VI-2); and

L⁵, L⁶, L⁷, and L⁸ each independently represent an alkyl group having 1to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, analkoxycarbonyl group having 2 to 5 carbon atoms, an acyl group having 2to 4 carbon atoms, a halogen atom, or a hydrogen atom, and at least oneof L⁵, L⁶, L⁷, or L⁸ represents a group other than a hydrogen atom.—Z⁵-T-Sp-P  Formula (VI-2)

In Formula (VI-2), P represents an acryl group, a methacryl group, or ahydrogen atom, Z⁵ represents —C(═O)O—, —OC(═O)—, —C(═O)NR¹— (where R¹represents a hydrogen atom or a methyl group), —NR¹C(═O)—, —C(═O)S—, or—SC(═O)—, T represents 1,4-phenylene, and Sp represents a divalentaliphatic group having 1 to 12 carbon atoms which may have asubstituent. However, one CH₂ in this aliphatic group or two or morenon-adjacent CH₂ may be substituted with —O—, —S—, —OC(═O)—, —C(═O)O—,or —OC(═O)O—.

The compound represented by Formula (VI) is preferably a compoundrepresented by Formula (VII).

In Formula (VII), Z¹³ represents —C(═O)— or —C(═O)—CH═CH—;

Z¹⁴ represents —C(═O)— or —CH═CH—C(═O)—; and

R¹³ and R¹⁴ each independently represent a hydrogen atom, a linear alkylgroup having 1 to 4 carbon atoms, a methoxy group, an ethoxy group, aphenyl group, an acryloylamino group, a methacryloylamino group, anallyloxy group, or a structure represented by Formula (IV-3).

Z¹³ represents —C(═O)— or —C(═O)—CH═CH— and is preferably —C(═O)—.

R¹³ and R¹⁴ each independently represent a hydrogen atom, a linear alkylgroup having 1 to 4 carbon atoms, a methoxy group, an ethoxy group, aphenyl group, an acryloylamino group, a methacryloylamino group, anallyloxy group, or a structure represented by Formula (IV-3), preferablyrepresents a methyl group, an ethyl group, a propyl group, a methoxygroup, an ethoxy group, a phenyl group, an acryloylamino group, amethacryloylamino group, or a structure represented by Formula (IV-3),and more preferably represents a methyl group, an ethyl group, a methoxygroup, an ethoxy group, a phenyl group, an acryloylamino group, amethacryloylamino group, or a structure represented by Formula (IV-3).

Specific examples of the compound represented by Formula (VI) are shownbelow. However, in the present invention, the compound represented byFormula (VI) is not limited thereto.

As the liquid crystal compound for use in the present invention, acompound represented by Formula (VIII) and described in JP2014-198814A,in particular, a polymerizable liquid crystal compound having two(meth)acrylate groups represented by Formula (VIII) is also suitablyused.

In Formula (VIII), A² and A³ each independently represent an alkylenegroup having 2 to 18 carbon atoms, and one CH₂ in the alkylene group ortwo or more non-adjacent CH₂ may be substituted with —O—;

Z⁵ represents —C(═O)—, —OC(═O)—, or a single bond;

Z⁶ represents —C(═O)—, —C(═O)O—, or a single bond;

R⁵ and R⁶ each independently represent a hydrogen atom or a methylgroup; and

L⁹, L¹⁰, L¹¹, and L¹² each independently represent an alkyl group having1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, analkoxycarbonyl group having 2 to 5 carbon atoms, an acyl group having 2to 4 carbon atoms, a halogen atom, or a hydrogen atom, and at least oneof L⁹, L¹⁰, L¹¹, or L¹² represents a group other than a hydrogen atom.

The compound represented by Formula (VIII) is preferably a compoundrepresented by Formula (IX).

In Formula (IX), n2 and n3 each independently represent an integer of 3to 6; and R¹⁵ and R¹⁶ each independently represent a hydrogen atom or amethyl group.

In Formula (IX), n2 and n3 each independently represent an integer of 3to 6, and it is preferred that n2 and n3 are 4.

In Formula (IX), R¹⁵ and R¹⁶ each independently represent a hydrogenatom or a methyl group, and it is preferred that R¹⁵ and R¹⁶ eachrepresent a hydrogen atom.

Specific examples of the compound represented by Formula (VIII) areshown below. However, in the present invention, the compound representedby Formula (VIII) is not limited thereto.

Such liquid crystal compounds can be produced by a known method.

(Chiral Agent (Chiral Compound))

The composition contains a chiral agent.

The type of the chiral agent is not particularly limited. The chiralagent may be liquid crystalline or non-liquid crystalline. The chiralagent may be selected from a variety of known chiral agents (forexample, as described in Liquid Crystal Device Handbook, Chap. 3, Item4-3, Chiral Agents for Twisted Nematic (TN) and Super Twisted Nematic(STN), p. 199, edited by the 142^(nd) Committee of the Japan Society forthe Promotion of Science, 1989). The chiral agent generally contains anasymmetric carbon atom; however, an axial asymmetric compound or planarasymmetric compound not containing an asymmetric carbon atom may also beused as the chiral agent. Examples of the axial asymmetric compound orthe planar asymmetric compound include binaphthyl, helicene,paracyclophane, and derivatives thereof. The chiral agent may have apolymerizable group.

The content of the chiral agent in the composition is preferably 0.5 to30% by mass with respect to the total mass of the liquid crystalcompound. The chiral agent is preferably used in a smaller amount, as ittends not to affect the liquid crystallinity. Accordingly, the chiralagent is preferably a compound having a strong twisting power in orderthat the compound could achieve twisted alignment of the desired helicalpitch even though its amount used is small.

Examples of such a chiral agent having strong twisting power include thechiral agents described in, for example, JP2002-302487A, JP2002-80478A,JP2002-80851A, JP2002-179668A, JP2002-179670A, JP2002-338575A,JP2002-180051A, JP1987-81354A (JP-S62-81354A), WO2002/006195A,JP2011-241215A, JP2003-287623A, JP2002-302487A, JP2002-80478A,JP2002-80851A, and JP2014-034581A, and LC-756 manufactured by BASFCorporation.

(Optional Components)

The composition may contain components other than the liquid crystalcompound and the chiral agent.

(Polymerization Initiator)

The composition may contain a polymerization initiator. In particular,in the case where the liquid crystal compound has a polymerizable group,the composition preferably contains a polymerization initiator.

The polymerization initiator is preferably a photopolymerizationinitiator capable of initiating a polymerization reaction uponirradiation with ultraviolet rays. Examples of the photopolymerizationinitiator include α-carbonyl compounds (as described in U.S. Pat. Nos.2,367,661A and 2,367,670A), acyloin ethers (as described in U.S. Pat.No. 2,448,828A), α-hydrocarbon-substituted aromatic acyloin compounds(as described in U.S. Pat. No. 2,722,512A), polynuclear quinonecompounds (as described in U.S. Pat. Nos. 3,046,127A and 2,951,758A),combinations of triarylimidazole dimer and p-aminophenyl ketone (asdescribed in U.S. Pat. No. 3,549,367A), acridine and phenazine compounds(as described in JP1985-105667A (JP-S60-105667A) and U.S. Pat. No.4,239,850A), and oxadiazole compounds (as described in U.S. Pat. No.4,212,970A).

The content of the polymerization initiator in the composition is notparticularly limited, but it is preferably 0.1 to 20% by mass and morepreferably 1 to 8% by mass, with respect to the total mass of the liquidcrystal compound.

(Alignment Control Agent (Alignment Agent))

The composition may contain an alignment control agent. The inclusion ofthe alignment control agent in the composition makes it possible toachieve stable or rapid formation of a cholesteric liquid crystallinephase. Further, depending on at least one of the selection of analignment control agent and/or a chiral agent or the selection of theconditions of a heat treatment or a cooling treatment in Step 2described later, a reflective layer 30 (a layer of a composition in acholesteric liquid crystalline phase state) having roughness on thesurface thereof, as shown in FIG. 3 described later, can be produced.

Examples of the alignment control agent include fluorine-containing(meth)acrylate-based polymers, compounds represented by General Formulae(X1) to (X3) described in WO2011/162291A, compounds described inparagraphs [0007] to [0029] of JP2012-211306A, compounds described inparagraphs [0020] to [0031] of JP2013-47204A, compounds described inparagraphs [0165] to [0170] of WO2016/009648A, the compounds describedin paragraphs [0077] to [0081] of WO2016/092844, and General Formulae(Cy201) to (Cy211) described in JP4592225B. The composition may containtwo or more selected from these compounds. These compounds can reducethe tilt angle of the molecules of the liquid crystal compound at theair interface of the layer, or align the molecules substantiallyhorizontally. In the present specification, the term “horizontalalignment” refers to that the long axis of the liquid crystal moleculeis parallel to the film surface, but does not require strictparallelism. In the present specification, the “horizontal alignment”means an alignment in which the tilt angle to the horizontal plane isless than 20°.

The alignment control agents may be used alone or in combination of twoor more thereof.

The content of the alignment control agent in the composition is notparticularly limited, but it is preferably 0.01 to 10% by mass, morepreferably 0.01 to 5% by mass, and still more preferably 0.01 to 1% bymass, with respect to the total mass of the liquid crystal compound.

(Solvent)

The composition may contain a solvent.

The solvent may be, for example, water or an organic solvent. Examplesof the organic solvent include amides such as N,N-dimethylformamide;sulfoxides such as dimethylsulfoxide; heterocyclic compounds such aspyridine; hydrocarbons such as benzene and hexane; alkyl halides such aschloroform and dichloromethane; esters such as methyl acetate, butylacetate, and propylene glycol monoethyl ether acetate; ketones such asacetone, methyl ethyl ketone, cyclohexanone, and cyclopentanone; etherssuch as tetrahydrofuran and 1,2-dimethoxyethane; and 1,4-butanedioldiacetate. These solvents may be used alone or in combination of two ormore thereof.

(Other Additives)

The composition may contain one or two or more other additives such asan antioxidant, an ultraviolet absorber, a sensitizer, a stabilizer, aplasticizer, a chain transfer agent, a polymerization inhibitor, anantifoaming agent, a leveling agent, a thickening agent, a flameretardant, a surface-active substance, a dispersant, and a colormaterial such as a dye and a pigment.

In the composition, it is preferred that one or more of the compoundsconstituting the composition are a compound having a plurality ofpolymerizable groups (a polyfunctional compound). Further, in thecomposition, the total content of the compound having a plurality ofpolymerizable groups is preferably 80% by mass or more with respect tothe total solid content in the composition. The solid content is acomponent for forming the reflective layer, and does not include asolvent.

By making 80% by mass or more of the total solid content in thecomposition into a compound having a plurality of polymerizable groups,in the case of forming the wave-like structure of the bright portion 14and the dark portion 16 of the cholesteric liquid crystalline phase, orfurther, in the case of forming the reflective layer 30 having periodicroughness on the surface shown in FIG. 3 to be described later, it ispreferable from the viewpoint that the wave-like structure of thereflective layer 30 (cholesteric liquid crystalline phase) or theroughness structure of the surface can be firmly fixed to impartdurability and the like.

In addition, the compound having a plurality of polymerizable groups isa compound having two or more immobilizable groups in one molecule. Inthe present invention, the polyfunctional compound contained in thecomposition may have liquid crystallinity or may not have liquidcrystallinity.

(Procedure of Step 1)

In Step 1, the above-described composition is first applied onto asubstrate. The application method is not particularly limited, andexamples thereof include a wire bar coating method, an extrusion coatingmethod, a direct gravure coating method, a reverse gravure coatingmethod, and a die coating method. Prior to application of thecomposition, a known rubbing treatment may be applied to the substrate.

If necessary, a treatment for drying the composition applied onto thesubstrate may be carried out after application. By carrying out thedrying treatment, the solvent can be removed from the appliedcomposition.

The film thickness of the composition (composition layer) applied ontothe substrate is not particularly limited, but it is preferably 0.1 to20 μm, more preferably 0.2 to 15 μm, and still more preferably 0.5 to 10μm, from the viewpoint of superior diffuse reflectivity of thereflective layer.

Next, the composition (composition layer) applied onto the substrate isheated to align the liquid crystal compound in the composition into acholesteric liquid crystalline phase state.

The liquid crystalline phase transition temperature of the compositionis preferably in the range of 10° C. to 250° C. and more preferably inthe range of 10° C. to 150° C. from the viewpoint of productionsuitability.

As preferable heating conditions, it is preferable to heat thecomposition at 40° C. to 100° C. (preferably 60° C. to 100° C.) for 0.5to 5 minutes (preferably 0.5 to 2 minutes).

In the case of heating the composition, it is preferable not to heat thecomposition to a temperature at which the liquid crystal compoundbecomes an isotropic phase (Iso). In the case where the composition isheated above the temperature at which the liquid crystal compoundbecomes an isotropic phase, defects of the cholesteric liquidcrystalline phase increase, which is not preferable.

<Step 2>

Step 2 is a step of cooling or heating the composition to form areflective layer so that the helical twisting power of the chiral agentcontained in the composition in the cholesteric liquid crystalline phasestate obtained in Step 1 increases by 5% or more. In other words, Step 2is a step of subjecting the coating layer to a cooling treatment or aheat treatment so that the helical twisting power of the chiral agentcontained in the composition constituting the coating layer (compositionlayer) formed on the substrate increases by 5% or more. As describedabove, by carrying out the present step, the twist of the liquid crystalcompound is further increased, and as a result, the alignment of thecholesteric liquid crystalline phase (inclination of the helical axis)is changed, whereby the bright portion 14 and the dark portion 16parallel to the substrate 10 are changed to form a reflective layer (alayer 12 b of a composition in a cholesteric liquid crystalline phasestate) having a bright portion 14 and a dark portion 16 having awave-like structure (uneven structure) as shown in FIG. 2.

Further, by selecting the conditions of the cooling treatment and theheat treatment in Step 2, it is also possible to form the reflectivelayer 30 having periodic roughness on the surface as shown in FIG. 3 bythe change in the alignment of the cholesteric liquid crystalline phase.

The helical twisting power (HTP) of the chiral agent is a factorindicating the helical alignment ability expressed by Equation (1).HTP=1/(length of helical pitch (unit: μm)×concentration of chiralagent)  Equation (1)

The length of the helical pitch refers to the length of the pitch P(=period of the helix) of the helical structure of the cholestericliquid crystalline phase in the composition and can be measured by themethod described on page 196 of the Liquid Crystal Handbook (publishedby Maruzen Co., Ltd.). The concentration of the chiral agent is intendedto refer to a concentration (% by mass) of the chiral agent with respectto the total solid content in the composition.

In addition, the value of HTP is influenced not only by the type ofchiral agent but also by the type of liquid crystal compound containedin the composition. Therefore, for example, in the case where acomposition containing a predetermined chiral agent X and a liquidcrystal compound A and a composition containing a predetermined chiralagent X and a liquid crystal compound B different from the liquidcrystal compound A are prepared, and the HTPs of both compositions aremeasured at the same temperature, the values may be differenttherebetween. Also, the value of HTP depends on the length of thehelical pitch formed in the composition, and the length of the helicalpitch can be appropriately adjusted depending on the temperature of thecomposition. That is, the length of the helical pitch can be adjusted bysubjecting the composition to a cooling treatment or a heat treatment.

The fact that the helical twisting power of the chiral agent increasesby 5% or more is intended to mean that an increase rate Z represented byEquation (2) is 5% or more in the case where the helical twisting powerof the chiral agent in the composition before cooling or heating thecomposition (layer of the composition) is taken as X and the helicaltwisting power of the chiral agent in the composition after cooling orheating the composition (layer of the composition) is taken as Y.Increase rate Z (%)={(Y−X)/X}×100  Equation (2):

The increase rate Z may be 5% or more and more preferably 10% or more.From the viewpoint of superior diffuse reflectivity of the reflectivelayer, the increase rate Z is more preferably 12% or more. The upperlimit of the increase rate Z is not particularly limited, but it isoften 30% or less.

In the present step, as described above, the composition is cooled orheated so that the helical twisting power of the chiral agent increasesby 5% or more. In particular, it is preferable to cool the composition.

In the case where the composition is cooled, it is preferable to coolthe composition so that the temperature of the composition drops by 30°C. or more, from the viewpoint of superior diffuse reflectivity of thereflective layer. Among them, from the viewpoint of superior effects, itis preferable to cool the composition so as to be lower by 40° C. ormore, and it is more preferable to cool the composition so as to lowerby 50° C. or more. The upper limit value of the reduction temperaturewidth of the cooling treatment is not particularly limited, but it isusually about 70° C.

In other words, the cooling treatment is intended to cool thecomposition so that the temperature of the composition is T−30° C. orless in the case where the temperature of the composition in thecholesteric liquid crystalline phase state before cooling is T° C.

The method of cooling is not particularly limited and may be, forexample, a method of leaving the substrate on which the composition isplaced in an atmosphere at a predetermined temperature.

The cooling rate in the cooling treatment is not limited, but in orderto suitably form the wave-like structure of the bright portion 14 andthe dark portion 16 of the cholesteric liquid crystalline phase, orfurther the roughness on the surface of the reflective layer which willbe described later, it is preferable to set the cooling rate to acertain degree of speed.

Specifically, the cooling rate in the cooling treatment is preferablysuch that the maximum value thereof is 1° C. per second or more, morepreferably 2° C. per second or more, and still more preferably 3° C. persecond or more. The upper limit of the cooling rate is not particularlylimited, but it is often 10° C. per second or less.

In addition, the helical twisting power of the chiral agent after thehelical twisting power increases by 5% or more is preferably 20 or moreand more preferably 30 or more. The upper limit thereof is notparticularly limited, but it is often 100 or less.

By setting the helical twisting power of the chiral agent to 20 or more,it is possible to suitably form the wave-like structure of the brightportion and the dark portion of the reflective layer.

Here, in the method for producing a reflective layer of the presentinvention, in the case where the composition layer (reflective layer) isexposed to wind, unevenness may occur in the surface state of thesurface of the reflective layer to be formed. Considering this point, inthe method for producing a reflective layer of the present invention, itis preferred that the wind speed of the environment in which thecomposition layer (liquid crystal layer) is exposed is low in all stepsof applying, heating, and cooling the composition. Specifically, in themethod for producing a reflective layer of the present invention, thewind speed of the environment in which the composition layer is exposedin all steps of applying, heating, and cooling the composition ispreferably 1 m/s or less.

In the case where the liquid crystal compound has a polymerizable group,in Step 2, the composition on the substrate may be subjected to a curingtreatment to fix the cholesteric liquid crystalline phase. That is, thecuring treatment may be carried out simultaneously with the coolingtreatment or the heat treatment.

The obtained reflective layer corresponds to a layer obtained by fixinga cholesteric liquid crystalline phase.

Here, as the state where the cholesteric liquid crystalline phase is“immobilized”, the most typical and preferred aspect is a state in whichthe alignment of the liquid crystal compound brought into a cholestericliquid crystalline phase is retained. The state where the liquidcrystalline phase is “immobilized” is not limited thereto, andspecifically, it refers to a state in which, in a temperature range ofusually 0° C. to 50° C. and in a temperature range of −30° C. to 70° C.under more severe conditions, this layer has no fluidity and can keep animmobilized alignment state stably without causing changes in alignmentstate due to external field or external force. In the present invention,as will be described later, it is preferable to immobilize the alignmentstate of a cholesteric liquid crystalline phase by a curing reactionproceeding upon irradiation with ultraviolet rays.

In the layer obtained by fixing a cholesteric liquid crystalline phase,it is sufficient that the optical properties of the cholesteric liquidcrystalline phase are retained in the layer, and finally the compositionin the layer no longer needs to show liquid crystallinity.

In addition, it is preferred that the immobilization of the cholestericliquid crystalline phase immobilizes the structure (alignment state) ofthe cholesteric liquid crystalline phase after the cooling treatment orthe heat treatment.

The method of the curing treatment is not particularly limited, andexamples thereof include a photo curing treatment and a thermal curingtreatment. Among them, a light irradiation treatment is preferable, andan ultraviolet irradiation treatment is more preferable. Further, asdescribed above, the liquid crystal compound is preferably a liquidcrystal compound having a polymerizable group. In the case where theliquid crystal compound has a polymerizable group, the curing treatmentis preferably a polymerization reaction by light irradiation(particularly ultraviolet irradiation), and more preferably a radicalpolymerization reaction by light irradiation (particularly ultravioletirradiation).

For ultraviolet irradiation, a light source such as an ultraviolet lampis used.

The irradiation energy amount of ultraviolet rays is not particularlylimited, but it is generally preferably about 0.1 to 0.8 J/cm². Theirradiation time of the ultraviolet rays is not particularly limited,but it may be determined as appropriate from the viewpoint of bothsufficient strength and productivity of the obtained layer.

In the above description, the procedure of applying the curing treatmentto the layer of the composition in Step 2 has been described, but Step 3may be carried out in which the composition is subjected to a curingtreatment to form a reflective layer obtained by fixing the cholestericliquid crystalline phase, after carrying out Step 2.

The procedure of the curing treatment is as described above.

<Reflective Layer>

According to the production method described above, a reflective layerin which the bright portion and the dark portion take a wave-likestructure, in the cross-sectional SEM observation diagram as shown inFIG. 2, is formed.

The reflective layer is a layer which has a cholesteric liquid crystalstructure and a structure in which the angle formed between the helicalaxis and the surface of the reflective layer periodically changes. Inother words, the reflective layer is a reflective layer which has acholesteric liquid crystal structure, in which the cholesteric liquidcrystal structure gives a stripe pattern of a bright portion and a darkportion in a cross-sectional view of a reflective layer observed by ascanning electron microscope, and therefore the angle formed between thenormal of the line formed by at least one dark portion and the surfaceof the reflective layer periodically changes. Therefore, the reflectivelayer of the present invention is capable of diffusing and reflectinglight in a substantially any direction, not in a limited direction.

JP2006-284862A discloses a method for producing an anisotropic opticalelement in which a composition containing a liquid crystal compound isapplied, heated to a temperature equal to or higher than the temperatureat which the liquid crystal compound is brought into an isotropic phase,and then a helical axis direction of a cholesteric liquid crystallinephase is inclined by lowering the temperature to a temperature at whicha liquid crystal compound becomes a cholesteric liquid crystalline phaseby blowing gas from a predetermined direction. The anisotropic opticalelement formed by this method manifests anisotropy in the reflection oflight but can reflect light only in a direction corresponding to theinclined direction of the helical axis, and does not exhibit gooddiffuse reflectivity as in the reflective layer according to the presentinvention.

In addition, a plurality of the reflective layers may be formed on thesubstrate.

For example, after forming the reflective layer X having a predeterminedselective reflection wavelength on the substrate by the above-describedmethod, the reflective layer Y having a selective reflection wavelengthdifferent from that of the reflective layer X may be formed by the sameprocedure. In the case of forming a plurality of reflective layers asdescribed above, it is preferable to laminate a plurality of layers inwhich a cholesteric liquid crystalline phase is immobilized using aliquid crystal compound having a polymerizable group.

Here, in the production method of the present invention, at least one ofthe selection of a chiral agent and/or an alignment control agent or theselection of the conditions of a heat treatment or a cooling treatmentis carried out, whereby it is possible to produce the reflective layer30 of the present invention having periodic roughness on the surface inaddition to having the wave-like structure (roughness structure) of thebright portion 14 and the dark portion 16 in the cross section, as shownin FIG. 3 conceptually showing the cross section, instead of areflective layer having a flat (substantially flat) surface (the surfaceon the side opposite to the substrate 10), as conceptually shown in FIG.2.

For example, by selecting a chiral agent having a large wave-likestructure inducing force inside the reflective layer 30, the wave-likestructure in the reflective layer 30 can be enlarged to make the surfaceof the reflective layer 30 uneven. Further, by selecting an alignmentcontrol agent having a weak anchoring effect on the surface of thereflective layer 30, it is possible to make the surface of thereflective layer 30 uneven as well. Further, by increasing thedifference between the heating temperature in Step 1 and the coolingtemperature in Step 2, the surface of the reflective layer 30 can bemade uneven as well. Further, by increasing the cooling rate in Step 2,the surface of the reflective layer 30 can be made uneven as well.

The reflective layer 30 of the present invention is a reflective layerobtained by fixing a cholesteric liquid crystalline phase, in which,similarly to the reflective layer shown in FIG. 2, a bright portion 14and a dark portion 16 of a cross section of a cholesteric liquidcrystalline phase formed by a helical structure of a cholesteric liquidcrystalline phase have a wave-like structure, and the reflective layer30 further has periodic roughness on the surface.

In the reflective layer 30 shown in FIG. 3, roughness (convexities) onthe surface is two-dimensionally formed (see FIG. 7).

Accordingly, the wave-like structure of the bright portion 14 and thedark portion 16 of the cross section of the reflective layer 30(cholesteric liquid crystalline phase) is formed not only in the lateraldirection shown in FIG. 3, but also, a similar wave-like structure isformed, for example, in the cross section in the direction perpendicularto the paper surface of FIG. 3. That is, the wave-like structure of thebright portion 14 and the dark portion 16 is observed in the reflectivelayer 30 in the cross section in all directions. Regarding this point,the same is true for the reflective layer shown in FIG. 2.

However, the present invention is not limited thereto, and thereflective layer may have a wave-like structure in which a continuouswave is formed only in one direction on the cross section or further onthe surface. However, from the viewpoint of the diffuse reflectivity, asdescribed above, the reflective layer 30 is preferably a structure inwhich the wave-like structure of the bright portion 14 and the darkportion 16 is observed in the cross section in all directions, orfurther, as shown in FIG. 7, the roughness on the surface istwo-dimensionally formed.

The roughness on the surface of the reflective layer 30 is periodic, butit is different from that of the wave-like structure of the crosssection. Specifically, the phase of the roughness on the surface of thereflective layer 30 is shifted by half (approximately half) from thewave-like structure of the cross section. Therefore, in the planardirection of the substrate 10, the position of the convex portion of thewave-like structure of the cross section of the reflective layer 30 isthe position of the concave portion of the roughness on the surface ofthe reflective layer 30, and the position of the concave portion of thewave-like structure of the cross section of the reflective layer 30 isthe position of the convex portion of the roughness on the surface ofthe reflective layer 30.

Further, as conceptually shown in FIG. 3, in the reflective layer 30,the pitch p1 of the surface roughness is basically equal to the pitch p2of the wave-like structure of the cross section. That is, in thereflective layer 30 of the present invention, the period of the surfaceroughness is equal to the period of the wave-like structure of the crosssection.

As shown in FIG. 3, the pitch p1 is the interval between the peaks ofthe convex portions on the surface of the reflective layer 30, and thepitch p2 is the interval between the peaks of the wave of the darkportion 16 closest to the surface of the reflective layer 30.

In addition, in the present invention, the fact that the pitch p1 andthe pitch p2 are equal to each other includes not only the case wherethe pitch p1 and the pitch p2 are completely identical, but also thecase where the pitch difference calculated by “[(p1−p2)/p1]×100” is ±30%or less.

In the reflective layer 30 shown in FIG. 3, the wave-like structure ofthe bright portion 14 and the dark portion 16 in the cross section ofthe reflective layer 30 (cholesteric liquid crystalline phase) is suchthat the pitch (period) of the wave is uniform, but the height of thewave is highest at the center (the central region) in the thicknessdirection of the reflective layer 30, and gradually decreases toward thesurface side in the thickness direction and toward the substrate 10.That is, the amplitude of the wave-like structure of the cross sectionof the reflective layer 30 is the largest at the center in the thicknessdirection and gradually decreases toward the surface side and thesubstrate 10 side.

Regarding the height of the wave in this wave-like structure, thereflective layer (the layer 12 b having a wave-like structure) having noroughness on the surface shown in FIG. 2 may also have the samestructure where the height gradually decreases from the center in thethickness direction to the surface side in the thickness direction andthe substrate 10. In addition, the wave-like structure of the reflectivelayer 30 having roughness on the surface thereof shown in FIG. 3 mayhave a structure having a wave with a uniform height over the entireregion in the thickness direction like the wave-like structure of thereflective layer shown in FIG. 2.

The reflective layer 30 having roughness on the surface as describedabove has a wave height (wave amplitude) of the wave-like structure ofthe bright portion 14 and the dark portion 16 due to the helicalstructure of the cholesteric liquid crystalline phase in the crosssection of the reflective layer 30 (cholesteric liquid crystallinephase) which is larger than that of the reflective layer with a flatsurface shown in FIG. 2. That is, in the case where the reflective layer30 has a large wave-like structure therein, the roughness thereof isalso transferred to the surface, so that the surface of the reflectivelayer 30 becomes rough in shape.

Therefore, the reflective layer 30 having roughness on the surface asshown in FIG. 3 can obtain higher diffuse reflectivity.

In order to obtain satisfactory high diffuse reflectivity in thereflective layer 30, it is preferable to narrow the pitch p2 of thewave-like structure of the cross section and to make the wave of thewave-like structure of the cross section large (high). Here, the stateof the roughness on the surface of the reflective layer 30 is greatlyinfluenced by the wave-like structure of the cross section. Therefore,in order to obtain satisfactory diffuse reflectivity in the reflectivelayer 30, it is preferable to narrow the pitch p1 of the roughness onthe surface and to increase (deepen) the height h of the roughness. Inparticular, as the height h of the roughness becomes higher, it tends toobtain higher diffuse reflectivity.

However, in the case where the pitch p1 of the roughness on the surfaceof the reflective layer 30 is narrowed, the height h of the roughnesstends to decrease, and in the case where the height h of the roughnessis increased, the pitch p1 of the roughness tends to narrow.

Considering this point, the pitch p1 of the roughness of the reflectivelayer 30 is preferably 0.5 to 10 μm and more preferably 1 to 6 μm.

The height h of the roughness of the reflective layer 30 is preferably 1to 500 nm, more preferably 5 to 300 nm, still more preferably 50 to 300nm, and particularly preferably 65 to 200 nm.

The thickness of the reflective layer 30 is also not particularlylimited and the thickness that satisfies the diffuse reflectivityrequired for the reflective layer 30 may be appropriately set accordingto the size in the planar direction of the reflective layer 30, thematerial for forming the reflective layer 30, and the like.

The thickness of the reflective layer 30 is preferably 0.3 to 20 μm andmore preferably 0.5 to 10 μm. By setting the thickness of the reflectivelayer 30 to 0.3 μm or more, satisfactory diffuse reflectivity can beobtained by the reflective layer 30 having a sufficient thickness.Further, by setting the thickness of the reflective layer 30 to 20 μm orless, unnecessary thickening of the reflective layer 30 can beprevented, for example, a projected image display member or the likewhich will be described later can be thinned

As described above, in the case where a plurality of reflective layersare provided on the substrate 10, the thickness per layer is preferablywithin this range. Further, the thickness of the reflective layer havingno roughness on the surface shown in FIG. 2 is also preferably in thisrange.

<Applications>

The reflective layer is a layer having a cholesteric liquid crystallinephase (cholesteric liquid crystal structure) having a predeterminedwave-like structure (hereinafter, the reflective layer is also referredto as “cholesteric liquid crystal layer”), and is preferably a layerobtained by fixing this cholesteric liquid crystalline phase.

The cholesteric liquid crystal layer is a layer showing selectivereflection characteristics with respect to light in a predeterminedwavelength range. The cholesteric liquid crystal layer functions as acircularly polarized selective reflective layer that selectivelyreflects either the dextrorotatory circularly polarized light or thelevorotatory circularly polarized light in the selective reflectionwavelength range and transmits the other sense circularly polarizedlight. A film including one or two or more cholesteric liquid crystallayers can be used for various purposes. In a film including two or morelayers of a cholesteric liquid crystal layer, the sense of circularlypolarized light reflected by each cholesteric liquid crystal layer maybe the same or opposite depending on the application. In addition, thecenter wavelength of selective reflection of each cholesteric liquidcrystal layer, which will be described later, may be the same ordifferent depending on the application.

In the present specification, the term “sense” for circularly polarizedlight means dextrorotatory circularly polarized light or levorotatorycircularly polarized light. The sense of circularly polarized light isdefined such that, in the case where light is viewed as it proceedstoward an observer and in the case where the tip of the electric fieldvector rotates clockwise as time increases, the sense is dextrorotatorycircularly polarized light, and in the case where it rotatescounterclockwise, the sense is levorotatory circularly polarized light.In the present specification, the term “sense” may be used for the twistdirection of the helix of the cholesteric liquid crystal. Selectivereflection by the cholesteric liquid crystal reflects dextrorotatorycircularly polarized light and transmits levorotatory circularlypolarized light in the case where the twist direction (sense) of thehelix of the cholesteric liquid crystal is right, whereas it reflectslevorotatory circularly polarized light and transmits dextrorotatorycircularly polarized light in the case where the sense is left.

For example, a film including a cholesteric liquid crystal layerexhibiting selective reflection characteristics in the visible lightwavelength range (wavelength of 400 to 750 nm) can be used as a screenfor projected image display and a half mirror. Further, by controllingthe reflection band, such a film can be used as a filter that improvesthe color purity of display light of a color filter or a display (forexample, see JP2003-294948A).

In addition, the reflective layer can be used for various purposes suchas a polarizing element, a reflective film, an antireflection film, aviewing angle compensating film, holography, and an alignment film,which are constituent elements of an optical element.

Hereinafter, the application as a projected image display member whichis a particularly preferable application will be described.

By the above-mentioned function of the cholesteric liquid crystal layer,a projected image can be formed by reflecting circularly polarized lightof either sense at the wavelength showing selective reflection among theprojected light. The projected image may be visually recognized as suchby being displayed on the surface of the projected image display memberor may be a virtual image which appears to float above the projectedimage display member as viewed from an observer.

The central wavelength λ of the selective reflection depends on thepitch P of the helical structure (=the period of the helix) in thecholesteric liquid crystalline phase and follows the relationship of theaverage refractive index n of the cholesteric liquid crystal layer andλ=n×P. Here, the center wavelength λ of the selective reflection of thecholesteric liquid crystal layer means a wavelength at the barycentricposition of the reflection peak of the circularly polarized reflectionspectrum measured from the normal direction of the cholesteric liquidcrystal layer. As can be seen from the above equation, the centerwavelength of the selective reflection can be adjusted by adjusting thepitch of the helical structure. That is, by adjusting the n value andthe P value, for example, in order to selectively reflect either thedextrorotatory circularly polarized light or the levorotatory circularlypolarized light with respect to the blue light, the center wavelength λis adjusted so that an apparent center wavelength of the selectivereflection can be set to a wavelength range of 450 to 495 nm.Incidentally, the apparent center wavelength of the selective reflectionmeans a wavelength at the barycentric position of the reflection peak ofthe circularly polarized reflection spectrum of the cholesteric liquidcrystal layer measured from the observation direction in practical use(in the case of being used as a projected image display member). Sincethe pitch of the cholesteric liquid crystalline phase depends on thetype of the chiral agent to be used together with the liquid crystalcompound or the added concentration thereof, a desired pitch can beobtained by adjusting these factors. As a method for measuring sense orpitch of helix, methods described in “Easy Steps in Liquid CrystalChemistry Experiment” p 46, edited by The Japanese Liquid CrystalSociety, Sigma Publishing, published in 2007, and “Liquid CrystalHandbook” p 196, Editorial Committee of Liquid Crystal Handbook, Maruzencan be used.

In addition, a projected image display member capable of displaying fullcolor projected images can be produced by preparing and laminatingcholesteric liquid crystal layers having an apparent center wavelengthof the selective reflection in the red light wavelength range, the greenlight wavelength range, and the blue light wavelength range,respectively.

By adjusting the center wavelength of the selective reflection of eachcholesteric liquid crystal layer according to the emission wavelengthrange of the light source used for projection and the mode of use of theprojected image display member, a clear projected image can be displayedwith high efficiency of light utilization. In particular, by adjustingthe center wavelengths of the selective reflection of the cholestericliquid crystal layer respectively according to the light emissionwavelength range of the light source used for projection or the like, aclear color projected image can be displayed with high efficiency oflight utilization.

In addition, for example, by configuring the projected image displaymember so as to have transmittivity to light in the visible lightregion, it is possible to provide a half mirror usable as a combiner ofa head up display. The half mirror for projected image display iscapable of displaying the image projected from the projector in aviewable manner, and in the case of observing the half mirror forprojected image display from the same surface side on which the image isdisplayed, it is possible to simultaneously observe information orlandscape on the opposite surface side.

EXAMPLES

Hereinafter, the features of the present invention will be described inmore detail with reference to Examples and Comparative Examples. Thematerials, the used amount, the ratio, the contents of a treatment, andthe procedures of a treatment described in Examples below may besuitably modified without departing from the spirit of the presentinvention. Accordingly, the scope of the present invention should not belimitatively interpreted by the specific examples described below.

Examples 1 to 3 and Comparative Examples 1 and 2 Example 1

(Preparation of Liquid Crystal Composition (1))

The following components were mixed to prepare a liquid crystalcomposition (1).

Rod-like liquid crystal compound 101 55 parts by mass Rod-like liquidcrystal compound 102 30 parts by mass Rod-like liquid crystal compound201 13 parts by mass Rod-like liquid crystal compound 202 2 parts bymass Polymerization initiator Irg819 4 parts by mass (manufactured byBASF Corporation) Chiral agent LC756 4.6 parts by mass (manufactured byBASF Corporation) Alignment control agent (1) 0.02 parts by massAlignment control agent (2) 0.03 parts by mass Methyl acetate 260 partsby mass Cyclohexanone 65 parts by mass

Rod-Like Liquid Crystal Compound 101

Rod-Like Liquid Crystal Compound 102

Rod-Like Liquid Crystal Compound 201

Rod-Like Liquid Crystal Compound 202

Alignment Control Agent (1)

Alignment Control Agent (2)

On the rubbed surface of a rubbed polyethylene terephthalate (PET)substrate (manufactured by FUJIFILM Corporation), the liquid crystalcomposition (1) was applied at room temperature using a wire bar so thatthe thickness of the coating layer (composition layer) after drying was5.0 μm. The coating layer of the liquid crystal composition was dried atroom temperature for 10 seconds and then heated in an atmosphere at 95°C. for 1 minute to align the liquid crystal compound. Thereafter, thecoating layer was irradiated with ultraviolet (UV) rays using a D bulb(lamp, 90 mW/cm²) manufactured by Fusion UV Systems, Inc. at an outputof 80% at 30° C. for 8 seconds, whereby the reflective layer 1 (whichcorresponds to the film formed by immobilizing the cholesteric liquidcrystalline phase) was formed on the PET substrate.

The transmission spectrum of the reflective layer 1 was measured using aspectrophotometer UV-3100PC (manufactured by Shimadzu Corporation), andthe reflective layer 1 had a selective reflection peak having a centerat a wavelength of 535 nm.

In the above procedure, after aligning the liquid crystal compound at95° C., the liquid crystal composition was cooled to 30° C. The coolingrate was 4.2° C./second at the maximum. The variation between HTP at thealignment temperature (95° C.) of the chiral agent in the liquid crystalcomposition and HTP at the immobilization temperature (30° C.) of thechiral agent in the liquid crystal composition cooled during UVirradiation was 17%. The variation is obtained by the following Equation(3).Variation={(HTP at immobilization temperature (30° C.) of chiral agentin liquid crystal composition)−(HTP at alignment temperature (95° C.) ofchiral agent in liquid crystal composition)/(HTP at alignmenttemperature (95° C.) of chiral agent in liquid crystalcomposition)}×100  Equation (3):

Further, in the case where the PET substrate having the reflective layer1 was set in a polarizing microscope so that the slow axis of the PETsubstrate coincided with the direction of the polarizer of thepolarizing microscope, and then the reflective layer 1 was observed, theformation of a diffraction grating-like structure (=undulated structure)was clearly confirmed (see FIG. 4).

In addition, it was confirmed that the layered structure of thecholesteric liquid crystalline phase was wave-like by cross-sectionalSEM observation (cross-sectional SEM photograph) of the reflective layer1 (see FIG. 5).

In each of the Examples, the helical twisting power of the chiral agentat the immobilization temperature was 20 or more.

Example 2

Reflective layer 2 was obtained in the same manner as in Example 1,except that the conditions of a heat treatment in an atmosphere at 95°C. (alignment temperature) for 1 minute were changed to a heat treatmentin an atmosphere at 85° C. (alignment temperature) for 1 minute.

It was confirmed that an undulated structure was formed also in thereflective layer 2, as in the case of the reflective layer 1. Further,the selective reflection peak of the reflective layer 2 was 533 nm.

Example 3

Reflective layer 3 was obtained in the same manner as in Example 2,except that the temperature at the time of UV irradiation(immobilization temperature) was changed from 30° C. to 40° C.

It was confirmed that an undulated structure was formed also in thereflective layer 3, as in the case of the reflective layer 1. Further,the selective reflection peak of the reflective layer 3 was 540 nm.

Comparative Example 1

The following components were mixed to prepare a liquid crystalcomposition (2).

Rod-like liquid crystal compound 201 80 parts by mass Rod-like liquidcrystal compound 301 20 parts by mass Polymerization initiator Irg819 3parts by mass (manufactured by BASF Corporation) Chiral agent LC756 5.5parts by mass (manufactured by BASF Corporation) Alignment control agent(2) 0.05 parts by mass Methyl ethyl ketone 230 parts by mass

Rod-Like Liquid Crystal Compound 301

On the rubbed surface of a rubbed polyethylene terephthalate (PET)substrate (manufactured by FUJIFILM Corporation), the liquid crystalcomposition (2) was applied at room temperature using a wire bar so thatthe thickness of the coating layer after drying was 4.5 μm. The coatinglayer of the liquid crystal composition was dried at room temperaturefor 10 seconds and then heated in an atmosphere at 90° C. for 1 minuteto align the liquid crystal compound. Thereafter, the coating layer wasUV-irradiated using a D bulb (lamp, 90 mW/cm²) manufactured by Fusion UVSystems, Inc. at an output of 80% at 35° C. for 8 seconds, whereby thereflective layer 4 was formed on the PET substrate.

The transmission spectrum of the reflective layer 4 was measured using aspectrophotometer UV-3100PC (manufactured by Shimadzu Corporation), andthe reflective layer 4 had a selective reflection peak having a centerat a wavelength of 540 nm. In addition, the variation between HTP at 90°C. (alignment temperature) of the chiral agent in the liquid crystalcomposition and HTP at 35° C. (immobilization temperature) of the chiralagent in the liquid crystal composition cooled during UV irradiation was1%.

Further, in the case where the PET substrate having the reflective layer4 was set in a polarizing microscope so that the slow axis of the PETsubstrate coincided with the direction of the polarizer of thepolarizing microscope, and then the reflective layer 4 was observed, theformation of a diffraction grating-like structure (=undulated structure)could not be confirmed.

The above results are summarized in Table 1 below.

The following evaluation of microscopic observation was carried outaccording to the following standards.

“A”: Undulated structure is clearly visible

“B”: Undulated structure is visible

“C”: There is no undulated structure

In addition, in Table 1, the “Alignment temperature” is a temperature atwhich the liquid crystal compound is aligned and corresponds to theheating temperature in Step 1 above. The “Immobilization temperature” isintended to refer to a temperature at the time of UV irradiation andcorresponds to the cooling temperature in Step 2 above.

In addition, the “HTP variation (%)” in Table 1 is a value obtained bythe following Equation (4).HTP variation (%)={(HTP at immobilization temperature of chiral agent inliquid crystal composition)−(HTP at alignment temperature of chiralagent in liquid crystal composition)/(HTP at alignment temperature ofchiral agent in liquid crystal composition)}×100  Equation (4):

TABLE 1 Alignment Immobilization HTP Microscopic temperature temperaturevariation observation (° C.) (° C.) (%) results Example 1 95 30 17% AExample 2 85 30 15% A Example 3 85 40 11% B Comparative 90 35  1% CExample 1

Comparative Example 2

According to Example 1 of JP2005-49866A, a glass substrate with analignment film, in which the surface of the alignment film was notsubjected to a rubbing treatment, was produced. The liquid crystalcomposition (2) was applied by spin coating onto the alignment film sothat the thickness after drying was 4.5 μm. After heating the coatinglayer of the liquid crystal composition in an atmosphere at 90° C. for 1minute to align the liquid crystal compound, the coating layer wasUV-irradiated using a D bulb (lamp, 90 mW/cm²) manufactured by Fusion UVSystems, Inc. at an output of 80% at 35° C. for 8 seconds to obtain areflective layer 5 on a glass substrate with an alignment film. The HTPvariation (%) was calculated in the same manner as described above andwas found to be less than 5%.

<Evaluation of Diffuse Reflectivity>

Using the double beam measurement mode of GCMS-3B manufactured byMurakami Color Research Laboratory Co., Ltd., the relative reflectanceof each reflective layer with respect to the reference (white plate) wasmeasured. Specifically, as shown in FIG. 6, incident light is irradiatedfrom the light source 20 from the normal direction of the surface of thesample (reflective layers 1 to 5) 22, and the relative reflectance wasmeasured by a detector 24 arranged at a polar angle θ of 40° or 60° withrespect to the normal direction of the surface of the sample 22.

The results are summarized in Table 2.

TABLE 2 40° direction 60° direction Example 1 45% 17%  ComparativeExample 1  0% 0% Comparative Example 2 13% 4%

As shown in Table 2, it was confirmed that, in the case of thereflective layer having an undulated structure, the relative reflectancein the 40° direction and the 60° direction was high and the diffusereflectivity was excellent.

Although not shown in Table 2, it was confirmed that the reflectivelayers 2 and 3 described in Examples 2 and 3 exhibited better diffusereflectivity than the reflective layers 4 and 5 described in ComparativeExamples 1 and 2.

Examples 4 to 6, and Comparative Example 3

<Preparation of Liquid Crystal Composition>

The components shown in Table 3 below were mixed to prepare liquidcrystal compositions (3) to (5). The amounts of the respectivecomponents are all parts by mass.

TABLE 3 Liquid crystal composition (3) (4) (5) Rod-like liquid crystalcompound 201 85 90 80 Rod-like liquid crystal compound 202 15 Rod-likeliquid crystal compound 203 10 20 Polymerization initiator Irg819 4 4 4(manufactured by BASF Corporation) Chiral agent (1) 5 5 5 Alignmentcontrol agent (3) 0.06 0.06 0.06 Methyl ethyl ketone 200 200 200Cyclohexanone 200 200 200

Rod-Like Liquid Crystal Compound 203

Chiral Agent (1)

Alignment Control Agent (3)

Example 4

Reflective layer 6 was obtained in the same manner as in Example 1,except that the liquid crystal composition (3) was used in place of theliquid crystal composition (1), and the conditions of the heat treatmentfor 1 minute in an atmosphere of 95° C. (alignment temperature) werechanged to a heat treatment for 1 minute in an atmosphere at 100° C.(alignment temperature).

It was confirmed that an undulated structure was formed also in thereflective layer 6, as in the case of the reflective layer 1. Further,the reflective layer 6 had a peak of reflection in the range of 450 to650 nm.

Example 5

Reflective layer 7 was obtained in the same manner as in Example 1,except that the liquid crystal composition (4) was used in place of theliquid crystal composition (1), and the conditions of the heat treatmentfor 1 minute in an atmosphere of 95° C. (alignment temperature) werechanged to a heat treatment for 1 minute in an atmosphere at 100° C.(alignment temperature).

It was confirmed that an undulated structure was formed also in thereflective layer 7, as in the case of the reflective layer 1. Further,the reflective layer 7 had a peak of reflection in the range of 450 to650 nm.

Example 6

Reflective layer 8 was obtained in the same manner as in Example 1,except that the liquid crystal composition (5) was used in place of theliquid crystal composition (1), the conditions of the heat treatment for1 minute in an atmosphere of 95° C. (alignment temperature) were changedto a heat treatment for 1 minute in an atmosphere at 80° C. (alignmenttemperature), and the temperature at the time of UV irradiation(immobilization temperature) was changed from 30° C. to 40° C.

It was confirmed that an undulated structure was formed also in thereflective layer 8, as in the case of the reflective layer 1. Further,the reflective layer 8 had a peak of reflection in the range of 450 to650 nm.

Comparative Example 3

Reflective layer 9 was obtained in the same manner as in Example 1,except that the conditions of the heat treatment for 1 minute in anatmosphere of 95° C. (alignment temperature) were changed to a heattreatment for 1 minute in an atmosphere at 85° C. (alignmenttemperature), and the temperature at the time of UV irradiation(immobilization temperature) was changed from 30° C. to 70° C.

In the reflective layer 9, no undulated structure was formed.

<Evaluation>

For each of the produced reflective layers of Examples 4 to 6 andComparative Example 3, the HTP variation was calculated in the samemanner as in Example 1 and the microscopic observation results wereevaluated (evaluation of the wave-like structure (layered structure) ofthe cross section of the reflective layer).

Also, a reflective layer was set on a spectrophotometer V-670(manufactured by JASCO Corporation) equipped with an absolutereflectance measuring system with the produced reflective layer facingthe light source side, and the height of the reflection performance at45° was evaluated under 0° incident and 45° detection conditions. Thereflection performance at 45° was evaluated by preparing a graph of thewavelength on the horizontal axis and the reflectance on the verticalaxis, removing the reflectance originating from the substrate,calculating the area of the reflection peak in the region of 500 to 650nm corresponding to the selective reflection wavelength of thereflective layer (cholesteric liquid crystalline phase), and then takingthe size of this area as the amount of reflection at 45°.

The results are shown in Table 4 below.

TABLE 4 Alignment Immobilization HTP Microscopic Amount of temperaturetemperature variation observation reflection Composition [° C.] [° C.][%] results at 45° Example 4 (3) 100 30 19 A 3.5 Example 5 (4) 100 30 20A 7.5 Example 6 (5) 80 40 8.6 B 1.1 Comparative (1) 85 70 3.7 C 0Example 3

As shown in Table 4, as compared with Comparative Example 3 having noundulated structure, it was found that the reflective layers of Examples4 to 6 having an undulated structure had a large amount of reflection at45° and excellent diffuse reflectivity.

Examples 7 to 13, and Comparative Example 4

<Preparation of Liquid Crystal Composition>

The components shown in Table 5 below were mixed to prepare liquidcrystal compositions (A) to (G). The amounts of the respectivecomponents are all parts by mass.

TABLE 5 Liquid crystal composition (A) (B) (C) (D) (E) (F) (G) Rod-likeliquid crystal compound 101 55 55 55 55 55 55 Rod-like liquid crystalcompound 102 30 30 30 30 30 30 Rod-like liquid crystal compound 201 1313 13 13 13 13 85 Rod-like liquid crystal compound 202 2 2 2 2 2 2 15Polymerization initiator Irg819 4 4 4 4 4 4 4 (manufactured by BASFCorporation) Chiral agent LC756 (manufactured 4.5 4.5 4.5 by BASFCorporation) Chiral agent (2) 4.5 3.4 Chiral agent (3) 5.3 4.0 Alignmentcontrol agent (2) 0.02 0.02 0.02 0.02 Alignment control agent (3) 0.06Alignment control agent (4) 0.04 0.04 0.04 0.04 Alignment control agent(5) 0.06 Alignment control agent (6) 0.06 Methyl acetate 285 285 285 285285 285 285 Cyclohexanone 50 50 50 50 50 50 50

Chiral Agent (2)

Chiral Agent (3)

Alignment Control Agent (4)

Alignment Control Agent (5)

Alignment Control Agent (6)

Example 7

On the rubbed surface of a rubbed polyethylene terephthalate (PET)substrate (manufactured by Toyobo Co., Ltd.), the liquid crystalcomposition (A) was applied at room temperature using a wire bar so thatthe thickness of the coating layer (composition layer) after drying was3.4 μm. The coating layer of the liquid crystal composition was dried atroom temperature for 50 seconds and then heated in an atmosphere at 95°C. for 1 minute to align the liquid crystal compound.

Thereafter, the coating layer was irradiated with ultraviolet (UV) raysusing a D bulb (lamp, 90 mW/cm²) manufactured by Fusion UV Systems, Inc.at an output of 80% at 30° C. for 8 seconds, whereby the reflectivelayer 10 (which corresponds to the film formed by immobilizing thecholesteric liquid crystalline phase) was formed on the PET substrate.Also in the above procedure, after aligning the liquid crystal compoundat 95° C., the liquid crystal composition was cooled to 30° C. Thecooling rate was 4.3° C./second at the maximum.

The variation between HTP at 95° C. (alignment temperature) of thechiral agent in this liquid crystal composition (A) and HTP at 30° C. ofthe chiral agent in the liquid crystal composition (A) cooled at thetime of UV irradiation was 17%. The HTP variation was calculated in thesame manner as in Example 1.

Examples 8 to 13 and Comparative Example 4

Reflective layers 11 to 17 were produced in the same manner as inExample 7, except that the liquid crystal composition to be used and theapplication amount of the liquid crystal composition were changed.

Further, the HTP variation was calculated in the same manner as inExample 1.

<Evaluation>

The following evaluations were made on the reflective layers 10 to 16produced in Examples 7 to 13 and the reflective layer 17 produced inComparative Example 4.

<<Film Thickness>>

A part of the reflective layer was peeled off, and the film thickness ofthe reflective layer was measured with a shape measuring lasermicroscope VK-X200 (manufactured by Keyence Corporation) using a10×objective lens.

<<Roughness of Surface>>

The surface of the reflective layer was measured with a shape measuringlaser microscope VK-X200 (manufactured by Keyence Corporation) using a150×objective lens.

The measurement results were analyzed to measure the pitch p1 (cyclelength) of the roughness on the surface of the reflective layer and theheight h of the roughness on the surface.

FIG. 7 shows the surface analysis results of the shape measuring lasermicroscope in Example 11 (reflective layer 14). In addition,two-dimensional roughness was similarly formed on the surfaces of thereflective layers 10 to 13, 15, and 16 produced in Examples 7 to 10, 12,and 13 as well.

<<Internal Wave-Like Structure>>

The cross section of the reflective layer was cut with anultramicrotome, an appropriate pretreatment was carried out, and themeasurement was carried out using a SU8030 SEM manufactured by HitachiHigh-Technologies Corporation. The measurement results were analyzed tomeasure the maximum height (the inner roughness height) of the roughnessof the internal wave-like structure and the pitch p2 of the wave-likestructure.

The reflective layers 10 to 16 formed in Examples 7 to 13 exhibitedsignificant formation of a wave-like structure in the central portion inthe thickness direction. In each of the reflective layers, the pitch p2(length of period) of the wave-like structure was equal to the pitch p1(length of period) of the surface roughness.

FIG. 8 shows a cross-sectional SEM observation diagram of Example 13(reflective layer 16). In FIG. 8, the reflective layer 16 is a graystriped region at the bottom of the figure, and the white regionthereover is due to the convexity of the surface positioned on the farside in the figure with respect to the cross section. Similar wave-likestructures were observed in the reflective layers 10 to 15 produced inExamples 7 to 12.

<<Evaluation of Microscopic Observation>>

The evaluation of microscopic observation was carried out in the samemanner as in Example 1.

<<Reflective Performance>>

A reflective layer was set on a spectrophotometer V-670 (manufactured byJASCO Corporation) equipped with an absolute reflectance measuringsystem with the produced reflective layer facing the light source side,and the height of the reflection performance at 45° was evaluated under0° incident and 45° detection conditions.

The reflection performance at 45° was evaluated by preparing a graph ofthe wavelength on the horizontal axis and the reflectance on thevertical axis, removing the reflectance originating from the substrate,calculating the area of the reflection peak in the region of 500 to 650nm corresponding to the selective reflection wavelength of thereflective layer (cholesteric liquid crystalline phase), and then takingthe size of this area as the amount of reflection at 45°.

The results are shown in Table 6 below.

TABLE 6 Comparative Example 7 Example 8 Example 9 Example 10 Example 11Example 12 Example 13 Example 4 Liquid crystal composition (A) (A) (B)(C) (D) (E) (F) (G) Film thickness [μm] 3.4 3.9 4.6 4.1 3.9 4.6 3.5 3.9Height of surface roughness [nm] 25 41 47 55 69 87 117 1 Pitch ofsurface roughness [μm] 1.9 2.5 2.5 2.9 2.9 2.9 3.0 0.3 Height ofinternal roughness [nm] 102 139 176 153 202 280 331 — Alignmenttemperature [° C.] 95 95 95 95 95 95 95 95 Immobilization temperature [°C.] 30 30 30 30 30 30 30 30 HTP variation [%] 17 17 17 17 19 17 19 1Evaluation of microscopic observation A A A A A A A C Amount ofreflection at 45° 2.3 4.6 5.8 7.2 11.2 15.7 16.5 0

As shown in Table 6, the reflective layer of the present inventionhaving a wave-like structure therein and having surface roughness hashigh diffuse reflectivity, as compared with the reflective layer ofComparative Example 4 having no internal wave-like structure and nosurface roughness.

Further, the diffuse reflectivity is superior as the height of thesurface roughness is higher. That is, the reflection by the cholestericliquid crystalline phase becomes more dominant in the internalreflection than the surface. As described above, in the case where thereflective layer 30 has a large wave-like structure therein, theroughness thereof is also transferred to the surface, so that thesurface of the reflective layer 30 becomes rough in shape. In otherwords, in the case where roughness is formed on the surface, theinternal wave-like structure also becomes larger. As a result, thereflective layer having larger roughness on the surface has betterdiffuse reflectivity.

From the above results, the effects of the present invention areobvious.

EXPLANATION OF REFERENCES

-   -   10: substrate    -   12 a: layer of composition in cholesteric liquid crystalline        phase state    -   12 b: layer having wave-like structure    -   14: bright portion    -   16: dark portion    -   20: light source    -   22: sample    -   24: detector    -   30: reflective layer

What is claimed is:
 1. A reflective layer obtained by immobilizing acholesteric liquid crystalline phase, wherein, in a cross section of thereflective layer, a bright portion and a dark portion derived from thecholesteric liquid crystalline phase are wave-like, and a surface of thereflective layer has periodic roughness which is different in phase fromthe wave of the bright portion and the dark portion of the cross sectionof the reflective layer.
 2. The reflective layer according to claim 1,wherein the roughness on the surface is formed by changing the alignmentof the cholesteric liquid crystalline phase.
 3. The reflective layeraccording to claim 1, wherein a pitch of the roughness on the surface is0.5 to 10 μm.
 4. The reflective layer according to claim 1, wherein aheight of roughness on the surface is 1 to 500 nm.